1. Field of the Invention
This invention relates to an automatic developing device which can develop with great accuracy a resist provided on a substrate to be treated.
2. Description of the Prior Art
In forming the pattern on a photomask or semiconductor wafer, a lithography step is performed. In this lithography step, patterning is carried out by applying a resist to the treatment substrate and using a particle beam such as an electron beam or selective exposure by an electromagnetic beam in a prescribed wavelength range, such as an ultraviolet beam, and the resist is then developed. Basically three methods of development may be employed: the spraying method, the dipping method and the puddling method.
In the spraying method, developer is sprayed onto the resist on the substrate under treatment. This method has the advantage that the developing step can easily be automated. However, temperature control of the developer is difficult and in addition, a temperature difference is produced in the developer in the surface of the substrate to be treated, due to the effect of the heat of vaporization. This tends to result in dimensional fluctuation of the resist pattern.
In the dipping method, the substrate to be treated, covered with the resist, is dipped in developer. This method has the advantage that the amount of developer used is small, and temperatures controllability is high, so the resist pattern shows comparatively slight dimensional fluctuation. However, this method is operationally inconvenient and difficult to automate successfully. Furthermore, dissolving of the resist pattern by the developer continues while the treated substrate is moved away after treatment. This has made it difficult to respond fully to increasingly severe demands for patterning accuracy. In addition, defects are easily produced by adhesion of particles suspended in the developer, making it difficult to form the prescribed resist pattern.
In the puddling method, a liquid film of developer is formed by dropping developer onto the resist while the substrate to be treated, on which the resist is provided, is either stationary or slowly rotating. This method may be considered as occupying an intermediate position between the spraying method and the dripping method. This is because, as in the dipping method, the amount of developer used is small, but it is easy to automate and the problems that occur in the dipping method, of dissolving of the resist continuing while the treated substrate is moved, of course do not arise. However, in this puddling method, temperature control of the developer during development is difficult, as it is in the spray process, tending to lead to appreciable fluctuation in the dimensions of the resist pattern.